The control of power to various electronic devices within a particular location has been achieved through the implementation of data communication over the location's power lines. Systems controlled in this manner include electronic appliances connected to electrical outlets, security alarm systems, garage door openers, lighting systems and the like. In general, a receiver is connected between the power line and each device to is be controlled, and at least one transmitter is connected to the power line. By utilizing the power line as the means for communication between the transmitters and receivers, such control systems may be installed without requiring the installation of additional wiring. Further, utilization of the power line also provides a greater physical range of control than may be available via infrared, ultrasonic or RF control systems.
Perhaps the most prevalent data protocol used today is what is known as the X-10 protocol developed by Pico Electronics of Fife, Scotland, and whose products are distributed in the United States by X-10 (USA) Inc. of Northvale, N.J. The X-10 power line data communication protocol is disclosed in U.S. Pat. Nos. 4,200,862, 4,628,440 and 4,638,299. Specifically, at a modulation frequency which is much greater than the 60 Hz AC signal, such as 120 KHz, the transmission of data is synchronized to the zero-crossing point of the AC power line. Each transmission is comprised of a start code (always set at 1110), an appliance or house code, and an operation or key code. The house code is composed of four bits representing the letters A through P. The key code is composed of five bits and either corresponds to either a number from one (1) to sixteen (16) or a particular operational command, such as ON, OFF, BRIGHT and DIM. The X-10 protocol supports up to 256 address codes as there are sixteen ( 16) letters and sixteen (16) numbers available as an address designation for an addressable device connected to the system. These 256 addresses are represented by A1-A16, B1-B16 . . . P1-P16.
To ensure data integrity, both the house codes and key codes of the X-10 protocol are actually transmitted in true and complement form on alternate half cycles of the power line. For example, if the letter B is represented by the house code 1110, the pattern 10101001 is actually transmitted as the house code. Thus, transmission of the four (4) bit start code, the four (4) bit house code, and the five (5) bit key code takes a total twenty-two (22) cycles.
The data signals transmitted using the X-10 protocol are generally of the form: EQU [address][address]. . . [function][function]
where ". . . " represents a pause or gap between transmissions of at least three (3) power line cycles in duration, "address" represents an address of a particular receiver and "function" represents the operation to be performed on the "address" transmitted. The "address" and "function" commands are each composed of a start code, a house code and a key code as described above and are repeated to ensure proper data integrity in the transmission. Further, several sets of "address" commands may be transmitted in succession such that the "function" command transmitted is applied to the preceding addresses transmitted. Thus, for example, to instruct receivers identified as A1 and A2 to be turned off, the following data pattern is transmitted: EQU [A1][A1]. . . [A2][A2]. . . [Aoff][Aoff]
Upon receipt of this command by the receivers connected to devices A1 and A2, power to the devices is disconnected by the receiver. Commands other than [Aoff], such as [Aon] or [Dim] (to dim lights) may also be used.
The limitation of the X-10 protocol in supporting only up to 256 addresses poses problems for those installations, such as large hotels, where it is necessary to support a significant number of receivers in excess of 256. The X-10 protocol also includes the capability for an "extended code." The extended code, a key code represented by the bit pattern 01111, is to be followed immediately, i.e., there is no gap in transmission, by a series of 8-bit bytes with the first 8-bit byte identifying the number of data bytes to follow. Though not yet known to be implemented in any commercially available product, use of the extended code would result in data transmission of a structure similar to the following example: EQU [Aext][Nbyte][byte 1][byte 2]. . . [byte N]
where "Nbyte" is the number of 8-bit bytes of data, "byte 1" to "byteN", to follow. The use of the extended code of the X-10 protocol is believed to have been designed to increase the number of available commands beyond [Aon], [Aoff] and [Dim], However, the extended code compromises data integrity as there are no gaps between successive bytes transmitted, nor are "Nbyte" and the data bytes following repeated. Moreover, the extended code does not provide a readily apparent method for supporting more than 256 address codes.
Another power line communication control system directed toward the provision of a security system for a hotel is disclosed in U.S. Pat. No. 4,367,455. As presented, the communications protocol utilized is described as generating modulation signals at 120 KHz over the 60 Hz AC line frequency and, like the standard X-10 protocol, is also limited to the support of 256 devices. To accommodate more than 256 address codes for devices connected thereto, it is suggested that more than one modulation frequency be implemented, with each modulation frequency supporting 256 address codes. This approach requires additional manufacturing costs for the system as the system must support the generation and receipt of multiple modulation frequencies. For example, each receiver may be required to recognize a multitude of frequencies. Alternately, isolation filters may be strategically installed, such as one after each circuit breaker, to isolate the power line after the filter to be receptive to only a particular frequency. Use of isolation filters does not require that each receiver be sensitive to all frequencies, but may require that different sets of receivers, each receptive to a specific modulation frequency, be manufactured and installed. Therefore, it is desirable to provide a power line communication protocol which is able to support more than 256 address codes without requiring additional hardware (other than, of course, the provision of additional receivers and possibly transmitters) thereby limiting manufacturing costs.
Another disadvantage of prior art systems is the implementation of application specific integrated circuits (ASICs) in both the transmitters and receivers to perform the communications protocol. Though the use of ASICs assists in reducing manufacturing costs for a large volume over other electronic solutions, hardware implementation of the protocol also results in inflexibility in implementing new command codes as a new ASIC must be developed to accommodate the new protocol codes. Therefore, it is desirable to develop an electrical appliance control system which utilizes a microprocessor and associated software to afford the manufacturer or user greater flexibility in creating new commands to be transmitted, received and interpreted. For example, it may be desirable to implement a set of codes which correspond to various levels of dimming for lights connected to the control system as opposed to simply offering a DIM or BRIGHT command code. Additionally, the use of software is preferable as it provides a mechanism whereby the actual power line communication protocol may be changed if desired. For example, the same software may be utilized to support a system having a particular protocol which supports up to 256 address codes as may be used to support a system having a different communication protocol to support 4096 or more address codes.
Though power line communication protocols use various transmission standards to ensure that noise is not interpreted as a command, present power line control systems do not provide a mechanism whereby precautions are taken to ensure that a transmitted signal is received by the appropriate receiver. Thus, for example, should a utility company desire to command a household's water heater to be disconnected for load shedding purposes, and the power line is noisy or a temporary interruption of the provision of power occurs during transmission of that signal, the water heater will not be turned off (or back on). Therefore, it is desirable to provide an automatic refresh capability whereby the signal is continually transmitted at specified time intervals to ensure that the command is received regardless of the presence of temporary noise or power interruption in the power lines connected the transmitter to the receiver.
It is also possible for problems of longer duration than may be cured by an automatic refresh capability to occur with systems of the prior art. Under circumstances such as a long power interruption or the presence of noise over an extended period of time, an electrical appliance connected to the system may be left in an undesirable state. For example, an appliance may be left on for a longer period than desired. Therefore, it is desirable to provide a power line communication system which automatically determines that communication to the receivers of the system is operating improperly and to thereby instruct the electrical appliance to return to its default state, such as turning off the appliance connected to the receiver.
To assist in installing or maintaining of a power line communication system, a test transmitter and a test receiver are often provided for prior art systems. Generally, the test transmitter is one which, when electrically connected to system, generates a test signal. For example, the test transmitter Model No. 6269 offered by X-10 (USA) Inc. for use with its products continuously generates P1 on/off signals when the test transmitter is plugged into an electrical outlet of the power line communication system. To ensure that the test signal is being transmitted over the power line, a test receiver indicating signal strength, such as test receiver Model No. 6270 offered by X-10 (USA) Inc., is provided for electrical connection to the power line. In this manner, the user may be assured that it is possible for a data signal transmitted over the power line to be received by a receiver connected to the system. Specifically, if an error condition is detected, it is likely that excessive noise or spurious electronic signals are present along the signal transmission line.
However, such test transmitters and test receivers are not useful when attempting to determine whether a particular addressable device, such as a transmitter or a receiver, is operating properly as prior art test transmitters generate a special test signal to ascertain whether the transmission line is acceptable. For example, if a particular device connected to a receiver of the system does not respond as commanded by a transmitter of the system, it would be useful to ascertain whether the receiver or the transmitter, not the transmission line, is in proper working condition. Therefore, it is desirable to provide a test transmitter which is able to transmit any specified data signal to any receiver connected to the system and to provide a test receiver which can "listen" to the data signals transmitted over the power line and provide a visual or audible indication of the received signal. In this manner, the receivers and transmitters themselves may be tested. Additionally, given the multitude of receivers and transmitters connected to the system, it is also desirable to provide portable test transmitters and receivers and to provide a means for selecting the address to which a command is to be transmitted or for which a signal is to be monitored. Finally, rather than a test receiver simply indicating an error condition as is known in the art, it is desirable to provide a visual display which displays the data signal received by the test receiver. Such a display may also be desirable for a test transmitter so that the operator can verify that the data signal transmitted is the same as was intended and programmed by the operator.
As stated above, electrical appliance control systems require that each device connected to the system that is to be individually controlled be uniquely identified. Thus, a means is provided with each receiver for selecting the designated address code of a particular receiver for controlling a device connected to the receiver. Transmitters connected to the system may also have an address code associated therewith as well. For example, the receivers of U.S. Pat. No. 4,200,682 utilizes two sixteen-position rotary switches for the selection of the address of the receiver--one rotary switch for selection of the house code and another rotary switch for selection of the device or key code of the X-10 protocol. The switches of U.S. Pat. No. 4,200,682 allow up to 256 address codes to be utilized in the system. Similarly, the receivers of U.S. Pat. No. 4,418,333 each have two rotary switches for selection of the house and unit codes, respectively, with each switch having sixteen positions resulting in support for 256 addresses. The track lighting system of U.S. Pat. No. 5,072,216 utilizes two sixteen-position switches to allow a total of 256 unique address codes to be set for the individual lights of the system.
In many applications, there are physical constraints as to the size of the receiver. For example, the receiver may comprise an electrical outlet and therefore must be of the same size as a standard outlet receptacle. If a system is to provide the capability to select a multitude of addresses, more switches or more complex switches having a greater number of switch positions may be required. Thus, increased addressing capability by using physical switches results in higher manufacturing costs and may result in a unit which exceeds the physical constraints of the unit's installation site.
Additionally, the provision of mechanical switches on each receiver and possibly on each transmitter provides a means for selecting the address of the unit which is easily accessible to the consumer. However, these switches are also accessible to those individuals not authorized by the consumer thereby allowing an unauthorized individual to improperly alter the address of the receiver/transmitter so that the system behaves in an undesirable manner or renders the system essentially inoperable. Therefore, it is desirable to provide a means for selecting the address code of each addressable unit connected to the system that does not utilize mechanical switches and which is not easily accessible to unauthorized personnel.